1. Field of the Invention
The present invention is concerned with toggle clamp constructions for clamping work pieces; in particular, its relates to such toggle clamps that are furnished with elements for confining the opening angle of the clamp arms of such mechanisms.
2. Description of the Prior Art
Clamp mechanism of the afore-described type have been disclosed, for example, by German Patent No. 136 16 441 C1 showing a so-called closed clamp head including an inquiry cassette adapted to be inserted in an engaging hole.
To confine the opening angle of the clamp arm of clamping mechanism of the afore-described type that can also consist of a clamp head opening in a fork-type way, German Patent Application No. 22 22 686 teaches to provide, within the end of the actuator cylinder facing away from the clamp head, a stop in the form of a pin serving as a path limiter for the piston moving during opening of the clamp mechanism toward the cylinder bottom, thereby defining the opening angle. The said pin can be axially adjusted by means of a bolt. Apart from the fact that such an adjustability by means of a bolt requires special sealing measures, the arrangement or assembly of such a stop means requires a special design at least of the bottom closure of the actuator cylinder, i.e. mass-produced or commercially available actuator cylinders cannot (readily) be used.
It is desirable that the clamp arm-opening angle of clap constructions of the afore-described type be adjustable because the opening angle of the clamp mechanism, for timing reasons, can be adjusted as large as necessary but as small as possible because in respect of timed finishing lines, for example, for the manufacture of car bodies or parts thereof, which is the principal field of application of clamping mechanisms of this type, the time required for opening and closing such a clamp mechanism is of decisive importance for the respective timed sequence.
It is, therefore, a primary object of the invention to so improve clamp mechanisms of the afore-described type that the adjustability of the limitation of the opening angle be insured independently of the actuator cylinder, and effected by means of a stop easily provided on the clamp head of the clamp construction in connection with the piston rod of the actuator cylinder.
A second object is to provide a new and improved clamp mechanism wherein the stop of the opening angle is to be adjustably arranged on the clamp head of the mechanism.
A third object of the invention is to provide a new and improved clamp construction wherein the opening position as reached is to be electrically displayed.
A further object of the invention is to provide a new and improved clamp mechanism wherein the gap or slot inherently provided on clamping mechanisms of this type be used on the clamp head to enable the stop to be accommodated therein.
The afore-going and other objects are attained with one aspect of the invention through a clamping mechanism comprising an actuator cylinder having a linearly guided piston rod in engagement with a header arranged on one end of the actuator cylinder, where it is connected, via an adjusting mechanism, to a clamp arm pivotally located on the header. In the area between the clamp arm and the actuator cylinder, the header includes an engaging hole, with an extension being provided on the piston rod of the actuator cylinder. In the practice of the invention, an element is detachably mounted in the engaging hole, which in cooperation with the extension of the piston rod forms a stop for limiting the opening angle of the clamp arm.
In the practice of the invention, the engaging hole anyway available in clamp assemblies of the afore-described type for the so-called end position inquiry cassette otherwise to be inserted therein, is used to insert therein and fix thereto, in lieu thereof, an element which together with the extension arranged on the piston rod of a correspondingly stable configuration, forms a stop for limiting the opening angle. Depending on the opening angle to be adjusted for the clamp arm, a correspondingly designed element is inserted into the engaging hole which defines the maximum path of displacement of the piston rod toward the pressure cylinder. A stock of elements designed in accordance with the path of displacement to be adjusted can be stored at the place of use of the clamp mechanism, to select therefrom the desired element in case of a switch-over of the clamp mechanism. However, by way of alternative it is preferred to provide an adjustable stop yet to be explained hereinafter.